In general, a linear relationship is probably most useful. Don't use
polynomial fits, especially for projections. If the amount increases (or
decreases) by a certain percentage each period, then you could use an
exponential relationship. Logarithmic or power law relationships are
sometimes useful, but I don't think they'll be useful for your purposes.

- Jon
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Jon Peltier
Peltier Technical Services, Inc.
http://peltiertech.com/



debbied wrote:
Can anyone help?

I have created an Excel chart showing by week the number of letter
submissions and now I want to forecast what will be received in the coming
weeks and show the forcast on the chart. How do I do this and what's the best
trendline to use. The letter submissions varies each week and can be anything
from 20 to 150